99563 - Turbulence Modeling M

Learning outcomes

The course aims to complete the basic knowledge related to the turbulent motion of a fluid in typical applications of energy engineering. In particular, situations of dynamic and thermal turbulence are analyzed in free flows and flows confined by walls of industrial interest. The course is also characterized by the introduction of advanced numerical methods that are used to solve conservation equations of convective-diffusive type that include several turbulence models. At the end of the course the student acquires knowledge regarding the use of turbulence models in numerical simulations of the DNS, LES and RANS type for incompressible flows.

Course contents

The course, divided into two modules (module I (lecture) and module II (laboratory tutorial)), deals with turbulence models for engineering. The course has classroom and laboratory lessons. Classroom lectures deal with theory relevant to understanding turbulence and models used in engineering applications. The laboratory tutorials allow the student to directly understand the various models that have been created for the computational simulation of this phenomenon.

Module 1 (Prof. Manservisi)

Part 1 - Introduction

Turbulent flows. Conservation equations for incompressible flows: conservation of mass, conservation of momentum, conservation of energy, approximation of Oberbeck-Boussinesq.

DNS (Direct Numerical Simulation) equations. Basic statistical definitions, random variables, random vectors, statistical description of turbulent flows.

LES (Large Eddy Simulation) equations. Basic of LES. Filtering and LES equations.

RANS (Reynolds-Averaged navier-Stokes) equations. The Reynolds-Averaged Navier-Stokes equation, Reynolds-Averaged energy equation, the turbulence closure problem.

Wall turbulence. Channel flow, pipe flow, law of the wall for velocity, law of the wall for temperature.

Part 2 - Turbulence modeling:

LES (Large Eddy Simulation) models. Basic of LES modeling. Smagorinsky-Lilly model, sub-grid models.

Eddy viscosity models. The k-ε model, the k-ω model, near-wall turbulence treatment and boundary turbulence conditions.

Eddy thermal diffusivity models. The kθ-εθ model,the kθ-ωθ model, near-wall thermal turbulence treatment

Algebraic models: algebraic stress and explicit algebraic heat flux models.

 

Module 2 (Prof. Cervone)

Part 3 - Introduction to numerical methods for CFD

• Space discretization of Partial Differential Equations
• Time discretization of advection-dominated PDE
• Combined space/time discretization
• upwinding techniques
  

Part 4 - Simulation in the lab

Basics of CFD simulation for turbulent flows. Selection of simulation parameters, numerical resolution setup and wall resolution.

The simulation in laboratory is performed with open-source packages:

- python (finite volumes CFD simulation)

- Libmesh (finite elements in-house turbulence models)

- OpenFOAM (RANS turbulence)

Readings/Bibliography

The course is based on teacher's notes. The notes and slides are available on https://virtuale.unibo.it

Teaching methods

Conventional classroom lesson and laboratory tutorials.

Teaching material: the teaching material presented in class will be made available to the student in electronic format via the internet. To obtain the teaching material: https://virtuale.unibo.it

In consideration of the type of activity and the teaching methods adopted, attendance of this training activity requires the prior participation of all students in modules 1 and 2 of training on safety in places of study, [https://elearning-sicurezza.unibo .it/] in e-learning mode

Assessment methods

Module 1

The exam consists of a written examination with three questions: one question regarding turbulence equations (part 1) and two questions on turbulence models (part 2)

Module 2

The exam consists of an oral presentation in which the student illustrates her/his own project on CFD simulation of a turbulent case (similarly to the tutorials in part 4).

Teaching tools

Personal computer and/or workstation in Lab.

Office hours

See the website of Sandro Manservisi

See the website of Antonio Cervone